Scalability Interview Questions - Medium

calendarDec 13, 2025 · 2 min read · scalability interview medium performance optimization  ·
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Medium-level scalability interview questions covering advanced scaling techniques and optimization.

Q1: Explain database partitioning strategies.

Answer:

Horizontal Partitioning (Sharding)

Range Partitioning:

Hash Partitioning:

Vertical Partitioning

Q2: How do you handle database hotspots?

Answer:

Problem: Uneven data distribution causing some shards to be overloaded.

Solutions:

Consistent Hashing with Virtual Nodes:

Q3: Explain the Thundering Herd problem and solutions.

Answer:

Problem: Many requests hit backend simultaneously when cache expires.

Solutions:

Request Coalescing:

Q4: How do you implement distributed caching?

Answer:

Cache Distribution Strategies:

Cache Invalidation:

Q5: Explain async processing and message queues.

Answer:

Use Cases:

Message Queue Patterns:

Q6: How do you handle session management at scale?

Answer:

Problem: Sticky sessions don't scale well.

Solution: Centralized session storage.

Session Storage Options:

Q7: Explain database connection pooling optimization.

Answer:

Pool Sizing Formula:

Connection Lifecycle:

Q8: How do you implement rate limiting at scale?

Answer:

Distributed Rate Limiting:

Sliding Window Algorithm:

Multi-Tier Rate Limiting:

Q9: Explain database query optimization techniques.

Answer:

Query Execution Plan:

N+1 Query Problem:

Denormalization for Read Performance:

Q10: How do you handle file uploads at scale?

Answer:

Chunked Upload:

Direct Upload (Presigned URL):

Summary

Medium scalability topics:

  • Partitioning: Range, hash, vertical strategies
  • Hotspots: Consistent hashing, caching solutions
  • Thundering Herd: Request coalescing, mutex locks
  • Distributed Caching: Consistent hashing, invalidation
  • Async Processing: Message queues, workers
  • Session Management: Centralized storage, JWT
  • Connection Pooling: Optimal sizing, lifecycle
  • Rate Limiting: Distributed, sliding window
  • Query Optimization: Indexing, denormalization
  • File Uploads: Chunking, direct upload, async processing

These techniques enable handling millions of users efficiently.

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